I thought I'd share this recent experience with some random crashes that I solved.
About 1 month ago my computer (running Windows 7 64 Bit for the past 18 months) started turning off. No warnings, no BSOD, no dump file etc. It just went "click" and turned off. After scouring various forums it seemed that I must be having a hardware problem. I checked everything except my power supply (an expensive Corsair) and it all seemed to be fine. Finally I looked in the Windows reliability monitor and noticed that the crashes started happening in Mid-September. I compared this with my Windows Update log and saw that a lot (10+) of updates were installed that day. I ran Restore using a time point from before the updates. And the crashes went away.
I have no idea which update might have caused the problem. I have been installing them 1 by 1 every day or so but the problem hasn't reoccurred.
My guess is that one of the updates didn't install correctly or was corrupted during download. I hope this helps someone else.